Fluid pressure servo mechanism



May 5, 1953 N. E. STARKEY FLUID PRESSURE sERvo MECHANISM 2 SHEETS-SHEET l Filed Aug. 26, 1950 M .G @Quanta t f%\ 2 SHEETS-SHEET 2 N. E. STARKEY FLUID PRESSURE SERVO MECHANISM May 5, 1953 Filed Aug. 2e, 195o Inventor: Neal E. Star'kel,

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I-Is Attorney.

Patented May 5, 1953 FLUID PRESSURE sERvo MECHANISM `Neal E. Starkey, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application August 26, 1950, Serial No. 181,651

2' Claims.

'This inventionrelates to fluid fuel regulating systems, particularly toa system for supplying two different types of fluid fuels toa thermal powerplant such as a gas turbine.

When a gas turbine powerplant is installed in alocality where natural gas is available, it is usually most economical toA arrange the powere plant to use such fuel to the maximum extent practicable, However, the availability of natural gas fuel varies from summer to winter, since in the winter' the consumption of gas for heating purposes lis greatly increased. Accordingly, it becomes necessary to provide the powerplant with a `dual fuel system capable of supplying either allnatural gas, or all some alternatefuel, or part -of each. It isl of course desirable that the change from one fuelto the other, or variation in the proportions in which the two fuels are supplied, be readily effected.

Accordingly, an object of the invention is to provide a dual fuel regulator for controlling the supply to a heat generator of gaseous fuel and a suitable liquid fuel oil, such as that sold commercially asV diesel fuel or the heavier residual oil known as Bunker C. A further object is to provide -a dual'fuel regulator of the type described in which the two fuels are supplied continuously in a fixed'ratio, regardlessfof wide variations inA the combined rate of supply. An-

other' object is to-provide a dual fuel regulator in which the ratio of one fuel to the other may be readilyaltered during operation, without even shutting down the powerplant.

Other objects and advantages will become apparentl from the following description taken in connection'with the 'accompanying drawings, in which Fig. l is a' diagrammatic representation of-a gas turbine.powerplanthaving a dual fuel system in accordance with the invention, and Fig. 2- is a Kmore detailed view, in section, of the fuel prcportioning regulator itself.

Generally, the fuel proportioning regulator which constitutes the essence of this invention isi-a hydraulic-mechanical servo-mechanism arrangedto receive an input signal pressure and to produce two outputsignal pressures, the arith metio sum of the output pressuresbeing pro portional to the inputsignalpressure and the ratio ofthe output pressures to each other being adjustable. rived from afuel regulator, which is not apart ofl they present invention, andthe two output sig nallpressures are employedto control -suitable la combustion system.

The inputsignal pressure is den Referring now more particularly to Fig.v 1, the fuel system is shown as applied to agas turbine powerplant of the simple "open-cycle type, comprising an axial flow compressor indicated generally at l, a combustion system comprising'va plurality of cylindrical -combustors spaced ciroumferentially around the axis ofthe power plant and indicated generally at 2, and an axial iiow turbine the exterior casing of which is indicated at 3. The compressor l takes air from the surrounding atmosphere through an intake casing ic and discharges directly into the combustors, from which hot motive uid enters the turbine 3 and leaves through an exhaust casing 3c. The precise structural details of the gas turbine are not material to an understanding of the present invention, but it may be noted that the powerplant shown is as disclosed in the copending appli-cation of Alan Howard, Chester S. Rice, and Bruce O. Buckland, Serial No. 754,002, filed June 1l, 1947, and assigned to the same assignee as the present application. This powerplant is a self-contained assembly, capable of being supported at its mid-portion by a pair of transversely spaced vertically extending links 4 pivoted at their lower ends to the foundation of the machine, athird point of supportbeing furnished by a fixed pedestal 5. With this three point support, the rather heavy compressor casing is in overhung relation to the supporting means, and an auxiliary support shown at 6 may be employed, principally to dampen vibration of the overhung compressor.

The powerplant auxiliaries comprise a suitable starting motor indicated in Fig. 1 as being an electric motor 'l coupled to the exhaust end of the turbine-compressor rotor. At theinlet end of the compressor are grouped a number of auxiliaries including a suitablev pump 8 for delivering the liquid fuel at a suitable. pressure, and a fuel regulator 9 adapted to provide the control signal pressure for determining the total amount of fuel to be supplied to the combustion system.

v The details of the regulator 9 are not material to an understanding of the present invention. but it is a hydraulic-mechanical servo-mechanism resposive to numerous operating characteristics of the powerplant, such as speed, motive fluid temperature, ambient atmospheric tempera-ture and pressure, and the position -of a control member which is set, either automatically or manually, to select the rate of fuelisupply desired. This last-mentioned control member is indicated in Fig. 1 as being a manual throttle lever 9d having oi idle, and full load positions. Regulators of this general type are disclosed in the copending application of Edwards, Garr, and Ogle, Serial No. 605,960, filed July 19, 1945, also the Ogle, Garr, and Edwards application Serial No. 697,058, led September 14, 1946, and the application of Starkey, Lewis, and Edwards, Serial No. 84,416, filed March 30, 1949. These regulators comprise means for integrating a rather large number of input signals and producing in accordance therewith a hydraulic output signal pressure which is a function of the rate of fuel supply desired. This signal pressure is represented by the symbol P1 hereinafter.

The liquid fuel oil is drawn by pump 8 from a reservoir (not shown) through an inlet conduit Il) and discharged through conduit II containing a fuel oil throttling valve I2. Conduit connects with an annular manifold I3 provided with a plurality of branch conduits, only one is shown at I4 communicating with a suitable fuel spray nozzle, indicated in dotted lines at I5. It will be appreciated that similar branch lines communicate with the respective nozzles in each of thev combustors. The fuel nozzles may be of any suitable type, but are preferably a single nozzle assembly having passages for receiving both the liquid and gaseous fuels and discharging them through a plurality of orifices so as to produce a desired spray pattern in the combustion space. Such dual fuel nozzles are known in the art, and the mechanical details thereof are not material to an understanding of the present invention. The natural gas or other gaseous fuel is received through a conduit I6 containing a fiow controlling valve |1 and communicating with an annular manifold I8 having branch conduits |9 supplying the respective fuel nozzles |5.

It will be appreciated from a consideration of Fig. 1 that the fuel oil control valve |2 comprises a flow control disc member |2a positioned by an expansible bellows |2b, the arrangement being such that the valve opens progressively as the control pressure within the bellows |2b increases. Thus the rate of supply of fuel oil to the manifold |3 is regulated by valve I2 in accordance with the control pressure P2 communicated to the bellows |2b. Likewise, the gas regulating valve |1 comprises a flow control disc member |1a positioned by a bellows |117, the rate of supply of fuel gas increasing as a function of the second control pressure Pa communicated to the bellows I1b.

The fuel proportioning regulator is indicated generally at 2B in Fig. 1, the details being shown more clearly in the sectional view of Fig. 2. This regulator comprises a housing 2| defining a chamber 22 vented to the atmosphere through a drain port 23. Chamber 22 has two transversely spaced portions 22a and 22h, the first containing a first pressure responsive bellows 24 and the other containing a second bellows 25. Housing 2| also defines a separate chamber 26 containing a third bellows 21.

Extending between the chambers 22a and 26 is a pilot valve bore 23 containing a longitudinally slidable main pilot spindle 29. This has a pair of axially spaced discs or lands 30, 3| deiining between them an annular space 32. As will be seen in Fig. 2, the upper end of spindle 29 engages the movable end abutment 21a of the fiexible bellows 21. The lower end of pilot spindle 29 is fixed, as by riveting, to the upper end abutment 24a of the flexible bellows 24. The upper land 3| of the main pilot spindle 28 4 arranged to cooperate with a drain port 3Ia, the port being opened as the land rises.

A secondary pilot valve includes a spindle 34 longitudinaly slidable in a bore 35 in housing 2| and having a pair of spaced lands 36, 31 defining an annular space 38 therebetween. At its upper end, spindle 34 is riveted to the end disc 25a of flexible bellows 25, and is connected by a pivot 39 at its mid-portion to a proportioning lever 40. The mid-portion of lever 40 is supported by an adjustable fulcrum in the form of a roller member 4| carried on an abutment 42 which may be positioned longitudinally in a groove 43 formed in the bottom wall of housing 2 I This axial positioning is effected by a lead-screw 44 carrying an adjusting thumb screw 45 exterior of housing 2|. It will be apparent that rotation of the adjusting screw 45 will turn the leadscrew 44 and cause the abutment 42 to move axially so that the fulcrum 4| may be positioned directly adjacent the auxiliary pilot spindle 34, or adjacent the main pilot spindle 29, or in any intermediate position. At its left-hand end, lever 40 carries an abutment 40a engaging the lower end disc 24h of bellows 24.

The hydraulic circuit; in the proportioning regulator 20 is as follows. The signal pressure P1 furnished by the fuel regulator 9 is communicated through conduit 46 to an annular cham- This signal pressure from conduit 46V ber 41. is communicated directly from the chamber 41 to the interior of the first bellows 21 by means of conduit 48, It will be apparent; that as the main pilot spindle 29 is displaced downwardly, the land 30 defines an annular orifice with the cut-off edge 41a for admitting oil under pressure into the annular chamber 32. This chamber is in communication with the interior of the second bellows 24 by way of a transverse drilled hole 49 communicating with a longitudinal drilled hole 50. Thus bellows 24 is charged with operating liquid at a variable pressure Pz in accordance with the position of pilot spindle 29, this pressure being communicated by way of conduit 5| with the bellows |21) of the fuel oil control valve |2. v

Oil under pressure from the conduit 46 is also supplied through a branch conduit 46a to a passage 52 in housing 2|, which passage is adapted to be blocked by the upper auxiliary pilot valve land 31. It will be apparent that upward move#- ment of pilot spindle 34 effects fiow of liquid under pressure from the passage 52 into the annular space 38, thence through port 53 and conduif, 54 to the space 26 surrounding the flexible bellows 21 and through conduit 54a to bellows 25, It will also be seen in Fig. 2 that the lower land 36 of the auxiliary pilot 34 cooperates with drain port 55 so that the drain port is uncovered when the land 36 descends. The pressure existing within the chamber 26 is the fuel gas control pressure, and is communicated by conduit 55 to the expansible bellows |1b of the fuel gas control valve.

The method of operation of the fuel proportioning regulator is as follows. In the inoperative or steady-state condition, illustrated in Fig. 2, the main pilot valve disc 30 just blocks the inlet port 41 and the upper land 3| blocks the drain port 3|a. Likewise, the auxiliary pilot valve disc 31 just blocks the inlet passage 52, and the lower disc 36 blocks the drain passage 55. If now the powerplant begins operation, the fuel regulator 9 will begin supplying a positive control signal pressure P1 to the conduit 46.

This .signal .pressure is communicatedk directly, by way of the generously proportioned ,annular space @land conduitll tothe signal pressure bellows 2l. The resulting force on the bellows end disc 2l@` forces the spindle 29 downwardly. This produces an annular orifice between the disc 3D andthe annular out-off edge ella,.through which pressure liauidfiiows into the space 32, thence through passages de, Ell into the bellows 24 so as to establish the fuel oilcontrol pressure P2 therein, and in the fuel oil control valve bellows i212.

The downward movementlof spindle 29, in combination with the pressure' P2 in bellows 2d, causes the pressure proportioning lever 4i) to pivotV counterclockwise about the fulcrum 4I. This causes the auxiliary yspindle 34 to rise, establishiing communication between the inlet passage 52 with the annular space til and conduit 54, so that the fuel gas control pressureP's is established in the space 26 actingV on the exterior of the bellows 2l and in the third bellow/S25. The pressure P3 acting on the lower surface of end disc lila tends to move it upwardly against the signal pressure P1. Likewise, the fuel gas control-pressure P3 lacting in bellows 25 tends to move spindle 315i downwardly. It will be seen that both of these effects tend to restore the proportioning lever 'le to an equilibrium position.

In the equilibrium condition,'it `will be ob- -1 served that the forces acting on the main pilot spindle ES result from the signal pressure P1 actingdownwardly on the bellows end disc 21a, the gas control pressure Pa acting upwardly on the end disc 27a, and the'oil control pressure P2 g:-

acting upwardly on the upper end disc 2M of bellows 24. rlhus, assuming that bellows M and 2l are of equal effective area, spindle 29 will be in an equilibrium position when the signal pressure P1 is the arithmetic sum of the fuel gas control pressure P3 and the fuel oil control pressure P2. If there is no leakage in the system, this equilibrium position will be reached with the disc 3l! just aligned with the annular cut-olf edge dla. if there should be some small lealeage somewhere in the system, the equilibrium position will be reached with a small orifice defined between disc 3o and edge fila, the orifice being of a size just suiiicient to supply the leakage so that the pressures P1, P2, .and P3 have the relation speciiled.

In order for the proportioning lever @il to be in an equilibrium condition, it is necessary that the oil control pressure 'P2 in bellows 2t, times the effective area of bellows 2li, times the moment arm between abutment lilla and fulcrum di shall equal the gas control pressure P3, times the effective area of bellows 25, times the moment arm from the pivot e9 tothe fulcrum 4l. Thusif it is again assumed that bellows '2M and 25 are of equal effective areas, the pressure P2 times its moment arm must equal the pressure Patimes its moment arm. In other words, the ratio of the fuel gas control pressure to the fuel oil control pressure must be a constant, as determined v and increases the pressure 113.3 supplied .to bellows 2.5.and the chamber 2li. These pressurefincreases effectthe restoring Aaction described above so that a new equilibrium condition is reached. Conversely when control signal .P1 decreases, bellows 2l contracts somewhat sov that `spindle 2.9 rises, theupper land 3l opens the drain port Bia, with the result that liquid drains from bellows through the passages '50, 9-32, 31a. The resulting decrease. in pressure P2 permits vthe balancing-lever lil to rotateslightly in the clockwise-direction so that spindle 34 descends to open portie land drain some liquid from the space 2li and bellows Q5, This reduced pressure in 25 and` 2t causes the auxiliary spindle 34` to krise until the drain port 55 is again blocked. Meanwhile the main spindle 29 descends slightly so that 'the drain port Ella is blocked.

Similarly, if the fuel gas control pressure P3 should suddenly decrease for some reason, bellows 425 will collapse so that spindle it rises to admit .more liquid from passage '52 until the pressure P3 is restored to the value required to balance pressure P2 acting on the other end of leverllil. rlhe same action will take place of course if the fuel oil control pressure P2 should suddenly increase.

'It will now be apparent that the bellows 2t, 2l lact on the main pilot spindle 2e under the influence of all three pressures P1, P2, P3 to insure that the sum of pressures P2, P3 will always equal the signal pressure P1. This means that the combined supply of fuel from the two sources will vary in direct relation to the input signal pressure received from the fuel regulator Similarly, the two fuel control pressures P2, P3 acting on the proportioning lever @lll insure that the two fuels will always be maintained at a preselected ratio to each other, as determined by the position of iulcrum 4I.

1i/Then fuel gas is cheap and plentiful, as may be the case in summer-time' in a gas-producing area, the variable ulcrum ill is positioned to the right by tur-nin the thumbscrew fli until the fuel oil control. pr sure P2 is insliicient to eifect opening oi the fuel oil control valve disc lgs against the inlet pressure ci the' fuel oil supplied by pump ii. The result 'isthat valve i2 will remain in closed position and the fuel gas control pressure P3 will positionthe' control valve El.

It will be understood, ofcourse, that both the mechanic-al characteristics@ the fuel control valves l2 and il', as well the fuel inlet pressures applied tothe respective valve discs ma, llo; will determine some minimum pressure which will be required in the actuating bellows Ib, lib before the respective fuel control valves will open. Thus when it is 'desired to operate entirely on. one fuel or the other, it is only necessary to adjust the proportioning'regulator 2d so that the proper control pressure, Pz or P3 as the oase may be, is below the minimum value required to open that fuel control valve. It will be apparent from the above discussion that moving the adjustable fulcruin il toward the right will decrease the amount of fuel oil supplied to the powerplant until it may become zero, operation being then entirely on fuel gas. Moving fulcrum il to the left will make. the fuel gas pressure decrease to zero, with operation entirely on oil. Thus in summer whenfuel gas is plentiful, .operation may be entirely .on that fuel, whereas in winter when the gas is required for other'purposes, operation maybe entirely on dieselfuel or'Bunker C oil. 'lirmost cases however it will be found economical in gas-producing regions to burn as large a proportion of fuel gas as the supply will allow, making up the balance of the fuel requirements from the more expensive fuel oil.

It will be apparent to those skilled in the art that many modifications of the structure shown in the drawings may be made. For instance, while the analysis of the operation has been described as if all three bellows 24, 25, 2l' were of equal effective area, it may be desirable in some cases to make these bellows of slightly different areas in order to obtain special operating characteristics as may be determined by analysis of' the conditions in a particular powerplant.

Also, it may be noted that, whereas the control signal pressure Pi furnishes both the input pressure signal through conduit 48 to bellows 21, and also the operating liquid for charging bellows 24, to establish the control pressures P2, P3, it is possible to supply the signal pressure Pi directly to bellows 21, and use a motive liquid from another independent source to supply conduit 46 for establishing the control pressures P2 and P3. However, the arrangement shown in Fig. 2 is ad vantageous since the single supply of hydraulic liquid from the fuel regulator 9 furnishes both the pressure signal and the motive fluid for establishing the control pressures.

It will also be obvious that many changes may be made in the specic mechanical details of the fuel proportioning regulator. Pressure responsive pistons or diaphragms might be used in place of one or more of the flexible bellows shown. Also the adjusting mechanism for varying the effective moment arms of the pressures P2, Ps on the balancing lever might take many forms. The arrangement of the respective housings for the bellows and pilot valves is not material to the present invention and could obviously take many other shapes.

While the invention has been described as a regulator for supplying one gas and one liquid fuel to a, gas turbine powerplant, it is obviously useful to supply two gaseous or two liquid fuels, and in other heat generators such as steam boilers or house heating systems.

Many other modifications will be apparent to those skilled in the art and it is desired to cover by the appended claims all such changes as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Hydraulic servo mechanism comprising a main pilot valve with a first movable member, rst expansible chamber means adapted to exert a force on said member proportional to a rst pressure, second expansible chamber means adapted to exert a force on said member in opposition to said first means proportional to a second pressure the main pilot member being adapted to control the flow of operating liquid to the second expansible chamber means to establish said second pressure therein, auxiliary pilot means having a second movable member, third expansible chamber means adapted to exert a force on said second movable member proportional to a third pressure, the auxiliary pilot member being adapted to control the flow of operating liquid to the third expansible chamber means to establish said third pressure therein, means for communicating the third pressure to the rst expansible chamber means in opposition to the first pressure, and lever means connecting said second movable member with said second expansible chamber means, whereby the main pilot member is positioned by the sum of the second and third pressures acting in opposition to the first pressure, and the second and third pressures are maintained in a preselected ratio to each other.

2. Hydraulic servo mechanism in accordance with claim 1 and including adjustable fulcrum means for the proportioning lever, whereby the constant ratio maintained between the second and third pressures may be varied.

3. Fluid pressure servo mechanism including a rst longitudinally slidable pilot valve member, first expansible chamber means with a movable member adapted to exert a force on said pilot valve member proportional to a signal pressure communicated to the first expansible chamber, second expansible chamber means having first and second movable end members the first of which is adapted to exert a force on said pilot valve in opposition to said signal pressure and proportional to a first control pressure, said first pilot valve having a portion adapted to control the flow of operating uid to the second expansible chamber means to establish said first control pressure therein, a second longitudinally slidable pilot valve member, third expansible chamber means having a movable end member adapted to exert a force on the second pilot valve member proportional to a second control pressure, said auxiliary pilot valve having a portion adapted to control the flow of operating fluid to the third expansible chamber means to establish said second control pressure therein, conduit means for communicating said second control pressure to the movable member of the first expansible chamber means in opposition to the signal pressure on said member, and lever means engaging a fulcrum and having spaced portions connected to the auxiliary pilot valve member and to the second movable end member of the second expansible chamber means, whereby the rst pilot valve is positioned in accordance with the sum of the first and second control pressures acting in opposition to said signal pressure and the control pressures are maintained in a preselected ratio to each other.

4. Fluid pressure servo mechanism comprising first pilot means including a first longitudinally slidable flow control member, first expansible chamber means including a movable abutment adapted to exert a force on said first flow control member in accordance with a signal pressure applied to one side of the abutment, second expansible chamber means having rst and second movable end abutment members one of which is adapted to exert a force on the first flow control member in opposition to said signal pressure and in accordance with a first control pressure supplied to the second expansible chamber, the first flow control member having a port-ion adapted to control the flow of operating fluid to the second expansible chamber to establish said first control pressure therein, second pilot means including a second longitudinally slidable pilot valve member, third expansible chamber means having a movable end member connected to exert a force on the second flow control member in accordance with a second control pressure, the second pilot having a portion adapted to control the flow of operatingr fluid to the third expansible chamber means to establish said second control pressure therein, and conduit means communicating the second control pressure to the first expansible chamber means to exert a force on the iirst movable abutment member in opposition to said signal pressure, and lever means engaging a ulcrum and having spaced portions connected to the auxiliary pilot valve member and the second abutment member of the sec-ond expansible chamber whereby the signal pressure and iirst and second control pressures position the first pilot member as a function of the sum of the control pressures opposing the signal pressure while the control pressures are maintained by the auxiliary pilot at a preselected constant ratio to each other.

5. Fluid pressure servo mechanism in accordance with claim 4 and including adjustable fulcrum means for the ratio control lever whereby the constant ratio maintained between the control pressures may be altered.

6. Fluid pressure servo mechanism comprising first pilot means including a rst longitudinally slidable spindle, a rst expansible bellows member enclosed in a housing with one end iixed relative thereto, the other end member of the bellows being adapted to exert a force on said first spindle in proportion to a signal pressure supplied to the interior of the bellows, a second bellows having a rst movable end member adapted to exert a force on the first spindle in opposition to the signal pressure in the rst bellows, said second bellows having also a second I movable end member, said first pilot spindle having iiow control portions adapted to meter operating uid to the second bellows to establish a first control pressure therein, second pilot means including a second longitudinally slidable spindle member, a third bellows having one end fixed and a free end member connected to exert a force on the second spindle proportional to a second control pressure supplied to the interior of the third bellows, said second pilot spindle having flow control portions adapted to regulate the supply of operating iiuid to the interior of said third bellows to establish the second control pressure therein, conduit means communicating said second control pressure from the third bellows to the housing surrounding the first bellows whereby the second control pressure acts on the movable end of the first bellows in opposition to said signal pressure, the first pilot member being positioned in accordance with the first and second control pressures acting in opposition to the signal pressure, lever means connecting the second pilot spindle with the second movable end member of the second bellows, and iulcrum means engaging an intermediate portion of said lever, whereby the second pilot spindle is positioned to maintain said first and second control pressures at a preselected constant ratio to each other in accordance with the position at which said fulcrum engages the lever.

'7. Fluid pressure servo mechanism comprising iirst pilot means including a first longitudinally slidable spindle member, a rst expansible bellows enclosed in a housing with one end i'iXed and the other end adapted to exert a force on said rst spindle in proportion to a signal pressure in the bellows, a second expansible bellows having first and second movable end members the rst of which is adapted to exert a force on said first spindle in opposition to said signal pressure, said first spindle dening a flow control portion adapted to regulate the supply of operating fluid to the interior of the second bellows to establish a first control pressure therein, second pilot means including a second longitudinally slidable spindle, a third expansible bellows having one end xed and a movable end adapted to exert force on said second spindle, said second pilot spindle having a flow control portion adapted to regulate the flow of operating fluid to the third bellows to establish a second control pressure therein, conduit means communicating said second control pressure to the housing surrounding the first 4bellows whereby said second control pressure acts on the movable end of the rst bellows in opposition to the signal pressure, and proportioning lever means engaging a fulcrum and connecting the second pilot spindle with said second movable end of the second bellows, whereby the second pilot is positioned to maintain the second control pressure at a preselected ratio to the rst control pressure in accordance with the position of said fulcrum.

NEAL E. STARKEY.

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